1. Field of the Invention
This invention relates to a camera.
2. Description of the Prior Art
There have been proposed many cameras of the type wherein a front housing which contains a photographing optical system, an exposure device, etc. is connected by a foldable connecting device such as a bellows or the like to a rear housing which contains a photosensitive material to be exposed to light, a view finder optical system, etc.; in photographing, the foldable connecting device is stretched to adjust the distance between the front and rear housings to a distance suitable for photographing; when the camera is not in use, the connecting device is contracted to bring the front and rear housings very close together to make the camera compact for improved portability.
Arrangement of this type is more often seen in so-called instant photograph cameras that use a sheet-like photosensitive material of a self-development processing type. An example of such a self-development-processing type sheet-like photosensitive material is disclosed in the specification of U.S. Pat. No. 3,682,076. According to this U.S. patent, a bag containing a self-development processing liquid is contained in the sheet-like photosensitive material. After exposure of the material to light, the bag containing the liquid is broken when the photosensitive material is carried to the outside of the camera passing between a pair of pressing rolls disposed inside the camera. Then, the development processing liquid is spread over the surface of the photosensitive material to effect a self-development process. A plurality of sheets of such a photosensitive material are piled up inside a film cartridge and the camera is loaded with the photosensitive material with the film cartridge placed inside a rear housing. In the case of a photosensitive material that is used for ordinary cameras, the material is used only for the purpose of forming thereon a negative image, which is then enlarged and is used for forming a positive image on printing paper. However, such a method does not apply to this self-development-processing sheet-like photosensitive material. A positive image is formed directly on the exposed photosensitive surface of the material; and the image is intended to be appreciated without being enlarged. Therefore, the surface of the photosensitive material must be sufficiently large for appreciation of the image formed thereon. For this reason, the size of the sheet-like photosensitive material of the self-development-processing type is arranged to be much larger than the sizes of 35 mm roll film, etc. Accordingly, the size of an instant photograph camera which uses such a photosensitive material is much greater than the ordinary camera that uses 35 mm roll film and is substantially disadvantageous in terms of portability.
In order to overcome such disadvantage, therefore, the instant photograph cameras in general are arranged to use a foldable connecting device such as bellows for connecting a front housing which contains a photographing optical system, an exposure device, etc. to a rear housing which contains the sheet-like photosensitive material, a view finder optical system, etc.; for photographing, the connecting device is stretched to adjust distance between the front and rear housings to a distance suitable for photographing; then, when the camera is not in use, the connecting device is contracted to bring the front and rear housings very close to each other to make the camera compact for carrying.
A camera of this type is divided into a front housing and a rear housing with a foldable connecting device such as bellows employed for connecting these two housings, because: In order to control light passing through a photographing lens which is provided in the front housing for exposure, an exposure device must be disposed in the front housing. On the other hand, it is generally required for a camera nowadays to have an automatic focussing device which permits automatic focussing without manual focussing adjustment so that a focussing failure that otherwise might result from manual adjustment can be prevented. However, where a camera is provided with such an automatic focussing device, the automatic focussing device is disposed in the front housing because it must be used for adjusting the position of the photographing lens on the optical axis thereof. Then, when the front housing thus arranged to contain various devices that must be disposed therein, the size of the front housing becomes large. In order to make the camera sufficiently compact, the rear housing is required to have some sort of accommodation to absorb an excessive portion in the front housing. Otherwise, it is impossible to make the camera sufficiently compact. However, the conventional cameras of the above stated type have been provided with no such accommodation for absorbing the excessively large size of the front housing.
Further, it has become very popular to provide a camera with an exposure control electric circuit using a photoelectric element. However, the above stated foldable type cameras are lagging behind other types of camera in respect to arrangement for automatic exposure control. To enable a camera of this type to perform automatic exposure control, a rear housing which contains, for example, a battery, a shutter circuit, etc. must be electrically connected to a front housing which contains a lens shutter to be controlled. In the case of a camera wherein no lens shutter is used, it is conceivable to automatically control a diaphragm disposed at the lens. Then, if the camera is provided with such an automatic diaphragm to be controlled, the front housing must be electrically connected to the rear housing. However, with electric wiring provided between the front and rear housings to connect them to each other in a foldable camera, the wiring hinders a foldable connecting device from being folded. Accordingly, this necessitates provision of a means for preventing such hindrance.
In order that a camera of the above stated type is made to be as small as possible, a power source battery which is provided for operating various mechanisms also must be as small as possible. Accordingly, in a camera which is equipped with, for example, an exposure control electric circuit, an automatic carrying-out device which automatically carries a sheet-like photosensitive material to the outside of the camera, an automatic focussing device, etc., it is desirable to provide a safety device which minimizes power consumption and prevents the power of the battery from being wasted by prohibiting the operations of these various devices when the camera is not loaded with the sheet-like photosensitive material. With such a safety device incorporated in the camera, however, it becomes difficult for the manufacturers, retailers or purchasers of the camera to test the actual performance and the operating accuracy of the camera without loading it with a photosensitive material. Thus, the use of such safety device makes it impossible to conduct ordinary tests. This is indeed great inconvenience.